EU Chief Brexit negotiator Michel Barnier answers to journalists upon his arrival at the European Council in Brussels on October 17, 2018.

BEN STANSALL | AFP | Getty Images

European Union negotiator Michel Barnier said on Friday a Brexit deal with the United Kingdom was 90 percent done, although there was still a chance no accord would be reached due to ongoing stumbling blocks over the Irish border.

"Ninety percent of the accord on the table has been agreed with Britain," Barnier told France Inter radio.

"I'm convinced a deal is necessary, I'm still not sure we'll get one," he said.

On Thursday, British Prime Minister Theresa May and other EU leaders voiced renewed confidence that they could secure a Brexit deal, yet the two sides remain at odds over how to deal with their only land border, between the British province of Northern Ireland and Ireland.

May had also signaled she would consider extending a so-called transition period "for a matter of months" after Britain leaves the EU in March.